Igor Zagorodniuk is a Ukrainian zoologist, mammalogist, ecologist, and founder of Theriological school. He is a laureate of the State Prize of Ukraine in the field of science and technology (2015), and the author of more than 500 scientific publications.

I. Zagorodniuk started his zoological research in ornithology when he was a student of Taras Shevchenko National University of Kyiv. His diploma project at University (and also the intermediate works) was devoted to the study of migrations and flying of birds.

Also, being a University student, I. Zagorodniuk started the study of amphibians (their hybrid zones in particular), conducted the experiments on biotope association of the amphibian group Bombina bombina – Bombina variegata, and also conducted experiments on the energy of Bombina species in winter time and the influence of wintering on the age structure of this species populations. At the same time, I. Zagorodniuk started the study of karyotypes of amphibians and rodents. When he began his work at I. I. Schmalhausen Institute of Zoology, the subject of his research was shifted towards the study of rodents. The first publication on this subject was devoted to the karyotypic variability of Microtus arvalis.

The results of this research became the basis of justification of the species independence for Microtus arvalis — M. obscurus. This became one of the results of PhD research by I. Zagorodniuk and the subject of the most cited publication by the scientist.

Taxonomic investigations make up a significant part of the scientific work of I. Zagorodniuk. This investigations were shifted from a description of small taxa to the group analysis and the discovery of patterns of formation and existence of low and high levels of taxonomic diversity. In this investigation, considerable attention is given to the groups of evolutionary and morphologically close species, primarily rodents. As a result of this cycle of research, 8 new taxa were described and a significant number of taxonomic permutations were proposed.

The following taxa are described as new to science:

Besides the taxa described for the first time, the researcher also substantiated the species, subfamily or generic statuses of a number of other taxa, which names were known as synonyms of other species or genera for a long period of time.

In the publications by I. Zagorodniuk a number of specifications are proposed regarding the interpretation of ranks and scopes of superfamily groups of mammals and unified names of some other taxa.